Lagoona Trenches

Lagoona Trenches are where underwater mining takes place. Located at the bottom of Lagoona Lake, this place is only accessible from the Underwater Mining Vessel in Lagoona Research Lab. Players can find a vast and varied amount of items hidden deep within undersea rocks. These treasures consist of fossils, Evolutionary Stones, and other rare commodities, such as Heart Scales, Rare Bones or pieces of Max Revive.

Underwater Mining Vessel
This is a small, yellow submarine that the player must operate in order to access the Lagoona Trenches. Talk to the blonde female scientist in the centre of Lagoona Lab and use an UMV Battery, in order to activate the UMV and dive underwater. The first time player arrives in Lagoona Lab, the blonde scientist will offer the player a free UMV Battery. When underwater, the right bar indicates the battery status of UMV Submarine. Driving around and mining causes the battery to deplete, and when the bar is empty, the player is sent back to Lagoona Lab. If the player has run out of batteries, he or she will either have to win a UMV Battery from Hobo's Lucky Lotto as a prize or buy more with Robux from that scientist in the following packs:

Note: The player is required to save before mining. This is to prevent players from using the free battery from trying again and again to get the items they want. If the game crashes or is suddenly disconnected, the player, unfortunately, cannot try again.

Shiny Spots
In order to find any items at all, the player must first find a shiny spot. These are a bright gold-yellow color, and star-shaped. They will appear upon cave walls, and spin around quickly while gradually getting smaller. They last only for a moment before it disappears back into the cave's wall again. However, it will appear again after a second, and repeats. If the player clicks on one of these spots, they will be able to start mining, where it is possible to find items.

Mining
The mining process is nearly identical to Sinnoh Underground in the core series games Pokémon Diamond, Pearl and Platinum, only with hammer switched for dynamites, and the pick changed to a drill. Find and click on sparkling parts of the wall to start mining. Like in real games, if the wall sustains too much damage before treasures are all dug out, it will collapse, destroying all treasures that are not retrieved in time. There is a green bar on top to show how much damage the wall has sustained, and the player must dig out all items before the bar fills up.

Each time the player mines, the number of items ranges between 1 to 4 inclusively. The treasures found are also similar to those in Sinnoh Underground, meaning that fossils, plates, certain kinds of evolutionary stones and some rare items can be found, but with the following changes:
 * The 4 fossils found in Unova and Kalos are added.
 * All kinds of spheres are removed.
 * The Pixie Plate is added.
 * New fossilized eggs are added. They can yield unique and rare Pokémon, including the Legendary "Lake Guardians".

Fossil Pokémon
Certain ancient Pokémon's fossils can be found within undersea rocks. Take these fossils to the back of Lagoona Lab, and talk to the male scientist near the fossil revival machine to reap the benefits of one's spoils. They are automatically set to Lv.10 upon revival. These fossils can also be traded to other Pokémon trainers when given to a Pokémon to hold. While having more Pokémon can always be beneficial, once the player collects them all, he or she should consider holding onto the rest in case he or she has a fossil others are looking for.

Fossilized Eggs
Different from normal fossils, these Pokémon are hatched from revived Fossilized Eggs found in underwater mining. The Fossilized Eggs are unique to this game. They are stored in the player's party or PC instead of his or her bag. The resurrection process is similar to other fossils — take the Fossilized Eggs to the back of Lagoona Lake Lab and talk to the male scientist for revival. Soft resetting does not alter the result. By obtaining from Fossilized Eggs, "Lake Guardians" Uxie, Mespirit and Azelf are the only Legendary Pokémon available in eggs.

Evolutionary Stones
Also found underwater are various Evolutionary Stones that can be used on specific Pokémon to help them evolve. With the exception of Oval Stone, all stones listed below are directly used on Pokémon to trigger evolution.

Other Treasures
There are a handful of other items that can be found via underwater mining. The rarity of these varies.

Trivia

 * As surprising as it may seem, Pokémon Eggs can actually be hatched underwater.
 * Some underwater treasures are very rare and have a very high value to other trainers, who might be willing to trade for them at the Trade Resort, accessible via the RTD.